And sticking with the Senate for another moment - today the leaders of the Senate Intelligence Committee provided an update on their investigation into Russian interference in last year's election. NPR's Ryan Lucas was on Capitol Hill and has more on what investigators say they've learned.

RYAN LUCAS, BYLINE: Since it opened its investigation in January, the committee has been trying to uncover and understand Russia's influence operation. One of the key questions - did the Trump campaign coordinate with Russia? On that, the committee's Republican chairman, Senator Richard Burr, would only offer this.

(SOUNDBITE OF PRESS CONFERENCE)

RICHARD BURR: The committee continues to look into all evidence to see if there was any hint of collusion. Now, I'm not going to even discuss initial findings because we haven't any.

LUCAS: Burr did say, however, that the committee agrees with the report that U.S. intelligence agencies released in January accusing Russia of interfering in the election. He also offered a big-picture view of Moscow's capabilities and the threat they pose to future American elections.

(SOUNDBITE OF PRESS CONFERENCE)

BURR: What I will confirm is that the Russian Intelligence Service is determined, clever. And I recommend that every campaign and every election official take this very seriously as we move into this November's election and as we move into preparation for the 2018 election.

LUCAS: Standing next to Burr in a packed Senate press conference, the committee's top Democrat, Senator Mark Warner, zeroed in on social media companies like Facebook and Twitter. The companies have faced intense public scrutiny in recent weeks over Russia's use of their platforms to influence Americans, particularly on divisive topics like race and immigration.

(SOUNDBITE OF PRESS CONFERENCE)

MARK WARNER: I was concerned at first that some of these social media platform companies did not take this threat seriously enough. I believe they are recognizing that threat now.

LUCAS: Facebook handed over copies of 3,000 Russia-linked ads to the committee this week. And Warner said the social media giants are generally cooperating with the inquiry. Investigators want to determine who paid for those ads and other ads and whether they targeted certain states or regions. They also want to find out whether Russian bots artificially amplified political conversations on Twitter. The committee has invited Twitter, Facebook and Google to an open hearing early next month. Ryan Lucas, NPR News, Washington. Transcript provided by NPR, Copyright NPR.